Is there another accurate global positioning system (GPS) other than the one established and maintained by the United States? Do the Russians and Chinese have their own satellite positioning systems?
My understanding is that the US system is highly accurate for civilian and military use. The military has the option to shut down the system regionally to prevent a hostile army from utilizing it.
Yet, it seems that in modern warfare GPS would be essential to a military. If a hostile military knew that it could not rely on the US satellites they would have to have a backup. What is the backup? How accurate is an alternative system compared to GPS?
Actually, it’s not the military’s decision. President Cinton (IIRC) signed into law that our precision signal would no longer be obfuscated. It would take an act of Congress or the President (not sure which) to start messing with it again.
Also, AFAIK, China’s system is not available for global use yet–they haven’t put up all the satellites required.
A modern Army doesn’t necessarily need GPS. It’s good for precision strikes and such, but depending upon the specific nature of the conflict, precision may not be critical.
AFAIK, the Selective Availability feature (the intentional degradation of the signal available to civilian receivers) was turned off by Clinton’s executive order in 2000, and would only require a new executive order to be turned on again.
If soldiers have gotten used to GPS or something like it, then loss of that resource could be a problem. OTOH, I presume they still teach map reading.
I’m a flight instructor and I teach a lot about GPS. Let me give you a few details about this, and then I have a question.
Prior to Clinton’s action, the GPS signal was available to civilian use, but it was degraded so as to be less accurate. When that changed, the full capability was available to all, and it has since been enhanced through WAAS (Wide Area Augmentation System). The accuracy with WAAS capability is now down to about 10 feet, and GPS has become the primary form of navigation for much (but not all) of aviation in the United States.
Since it’s authorized by the FAA as a primary source of navigation, it’s unlikely GPS would be turned off for any reason. But…
I have my doubts about this if it came to another 9/11. Something tells me that if there is a switch that would turn it off for civilians, they would do it regardless of the consequences for domestic air traffic. Call me paranoid, but what do we think about this?
At most they would go back to the less accurate system, IMO. There’s just too much out there that depends on GPS. The financial world, for one, uses the GPS time to regulate money transfers (at least, that’s what I’ve been taught). Shutting the system down entirely is very bad juju for more than just the aviation sector, and I just can’t see any president going down that road.
Being a flight instructor Mach Tuck, you should understand better than others that denying a hijacked commercial aircraft GPS isn’t going to ensure the hijackers miss their target. The inertials will get them there just fine (I’m assuming commercial aircraft still use them? I know we do in the military). Even a sectional would do the trick, assuming the weather cooperates. So denying GPS isn’t going to necessarily deny bad things from happening should another 9/11 roll around. At least, that’s my take on it.
I suspect, and hope, that you’re right. But what gives me pause is that a prospective hijacker isn’t too likely to understand how to use an inertial nav or VOR system when it’s so easy to just press “Direct To” on a handheld GPS unit.
That, and the penchant for the government to go batshit insane at the prospect of terrorism. I suspect there are those in government who DON’T realize the consequences of shutting down the GPS system, and would advocate doing so if they thought for a second it might prevent an attack. Again, maybe I’m paranoid…
Primary source but not normally sole source. Keep in mind that modern flight management systems fitted to commercial aircraft aren’t just a GPS, they use all available navaids to give a best computed position. An FMS may use 2 x DMEs for a position when available as that is theoretically more accurate than GPS. The thing is, from a piloting perspective, there’s no change to operating the FMS, so whether the FMS is currently using DME/DME or DME/VOR or GPS, or INS for its position, the “Direct To” whatever waypoint you want to go to still works the same way. Also modern GPS units are able to use alternative systems such as GLOSNASS where available.
If GPS was turned off, the effect would be worst in remote areas and minimal in highly populated areas.
I’m talking about non-U.S. forces using the system.
Besides, I don’t buy the tone of your post. Even U.S. forces could muddle by just fine without GPS. We’ve been doing it for decades before the system came along. Even your cite says
Exactly what I said earlier, and again, precision may not even be necessary depending upon the specific nature of the conflict. If that’s relying “heavily” on GPS, well, I’m not sure we’re using the term “heavily” correctly.
I don’t want to get into parsing the FARs too technically here, but there are certain flight conditions under which GPS could be the sole source of navigation for some aircraft. I’m thinking of a WAAS capable GA plane flying a stand-alone GPS approach into an airport with no other types of approaches (there are several such airports near me).
While the typical GA plane certainly could use VOR as a backup (diverting to an alternate airport in my scenario), my point is that for some purposes GPS is it, and in others it would still be a great inconvenience. And in the future we’ll be relying on it more and more. Turning off the signal for security reasons would be bad for a lot of people at that moment.
Again, I’m only speculating here. I find it an interesting, if unlikely, scenario to game out.
Yeah, probably the worse time would be in the middle of an approach. For enroute aircraft it would be annoying but not necessarily a big deal while an aircraft doing an RNAV approach would initially have to go-around and then could find itself with no airfields within range with a suitable approach. That’s when you start rummaging through the Jepps looking for a near by broadcast station that you can use as a makeshift NDB for a do-it-yourself approach (assuming the aircraft even has an ADF, many don’t these days).
I’m sorry you don’t like the tone. I’m merely reporting what information is publicly available. My military contacts tell me GPS is heavily integrated but they won’t share beyond that. While the US military may have gotten along just fine in the past without GPS does not mean they would be today. If GPS replaces old technology, and that old technology is no longer available/used, just because something worked in the past means nothing today.
Yes, you blindly looked around and threw in some links which it appears you didn’t read, then threw in some ‘military contacts’ for good measure. Good for you, back at ya.
In terms of “going back” to the less accurate system - I didn’t think that was possible since there have been new birds launched that don’t how the now-redundant obfuscation ability used to degrade the accuracy for non-US-military GPS units, although they could have said they don’t have the capability.
In terms of the military needing GPS… I think it was a general who said “a computer with a bullet hole is a paperweight, a map with the bullet hole is still a map”.
I’m not aware of the newer sats not having that capability. I’d be interested to read something to that effect, if you could point me in the right direction. It was my (admittedly dim) understanding that it was a software method one could initiate from the ground.
you missed a key part of the wiki article:
“Clinton’s executive order required SA to be set to zero by 2006; it happened in 2000 once the U.S. military developed a new system that provides the ability to deny GPS (and other navigation services) to hostile forces in a specific area of crisis without affecting the rest of the world or its own military systems.[72]”
so the new satellites don’t have the old SA mechanism, they may well have a new improved and classified method that can be turned on.